Blush coated fabric and method for producing the same

ABSTRACT

THE INVENTION IS A LEATHER-LIKE SHEET MATERIAL AND A METHOD OF MAKING IT, WHEREIN A CAST FILM OF A BLUSHABLE POLYURETHANE COATING IS DRIED BY EVAPORATION OF THE VOLATILE COMPONENETS. THE DRIED FILM, WHICH IS MICROPOROUS, MAY BE USED AS AN UNSUPPORTED FILM BY STRIPPING FROM A TEMPORAY SUPPORT, OR IT MAY BE USED ATTACHED TO A PERMANENT SUPPORT SUCH AS A TEXTILE FABRIC.

United States Patent 3,594,220 BLUSH COATED FABRIC AND METHOD FOR PRODUCING THE SAME Frederick H. Schwacke, Jr., Farmingdale, N.Y., John L. Egitto, Belleville, N.J., Charles A. Kumins, Chappaqua, N.Y., and Robert S. Hansen, Ames, Iowa, as-

signors to Inmout Corporation, New York, N.Y.

No Drawing. Continuation of application Ser. No. 464,578, June 16, 1965. This application May 14, 1969, Ser. No. 828,422

Int. Cl. D06n 3/00 U.S. Cl. 117135.5 28 Claims ABSTRACT OF THE DISCLOSURE The invention is a leather-like sheet material and a method of making it, wherein a cast film of a blushable polyurethane coating is dried by evaporation of the volatile components. The dried film, which is microporous, may be used as an unsupported film by stripping from a temporay support, or it may be used attached to a permanent support such as a textile fabric.

This is a continuation of our copending application Ser. No. 464,578, filed June 16, 1965, and now abandoned.

This invention relates to water vapor permeable coatings having a moisture vapor transmission comparable to that of leather and aims to provide new method of applying a tough breathable coating to a flexible porous base and a new composite material including a flexible porous dimensionally stable base having a surface coated with an adherent breathable film of elastomeric material. It is a particular object of our invention to provide improvements in materials which may be used as substitutes for leather, particularly the type of flexible leather that is used in the manufacture of garments and as uppers for boots and shoes, and in the preparation of such leather substitutes.

A good leather substitute should have several basic qualities:

( 1) A hand like that of leather;

(2) A breathability approaching that of leather;

(3) A good scuff or abrasion resistance;

(4) The ability to withstand rather wide variations in temperature without change;

(5 Good resistance to permanent deformation through bending or creasing;

(6) Good tear strength or resistance to tearing; and

(7) Its top or exposed surface should have no visible pores.

It is known that a material having these properties can be provided by coating a porous flexible base, such as a sheet of woven fabric, with an adherent breathable film of an elastomeric polyurethane. The term breathable is here used in the sense in which it is used in the leather industry to mean that it is able to transmit water vapor.

In the past, breathability has been imparted to such a polyurethane film by applying a solution of the polyurethane to the flexible porous base and then leaching with a liquid miscible with the solvent to remove the solvent. In such a process the leaching is usually accomplished by the immersion of the coated substrate in the leaching liquid. Such leaching processes are described in U.S. Pat. No. 3,169,885, copending application, Ser. No. 342,527, which is owned by the assignee of this application, and to which reference is made by permission, and Belgian Pat. No. 636,018.

The leached coatings so prepared are composed of elongated columnar cells filled with air providing essen "ice tially a macro-porous structure in which the cells have an average diameter of 20-200 microns. When a vertical cross-section of such a coating is examined closely under bright light, it will be found that at least 50% of the film of the coating is composed of cells visible to the unaided eye.

While the leaching process is capable of producing an acceptable leather substitute, it is subject to certain disadvantages, The apparatus used for leaching is relatively cumbersome requiring tanks for the leaching liquid and means for conveying the coated fabric through the leaching tanks. The leaching methods are also relatively slow. In addition, leaching involves the using of large quantities of leaching liquid usually water in proportion to the solvent removed. Because of the small proportion of the solvent present in the leaching liquid, solvent recovery is virtually impractical. This is particularly true when the leaching liquid is water from which most miscible solvents can be removed only with considerable difiiculty. In many cases where solvent recovery would be impractical, solvent removal is required in order to prevent contamination of community sewage disposal means.

We have discovered that an improved leather substitute can be prepared through a modification of the technique that has been practiced in the past in the preparation of blushed lacquer films. This blushing technique, as conventionaly practiced in the past, is well known (See U.S. Pat. Nos. 2,207,695, 2,262,270, 2,296,337, 2,299,991 2,306,525, 2,519,660 and 2,665,262). An ordinary blushed lacquer film is made from a normally transparent resinous material that is rendered opaque through the modification of its physical structure so that it will diffuse light. The physical structure of the resinous material is modified to subdivide it into numerous interconnected particles or to disperse a great number of microscopic cells therein by dissolving it in a mixture of volatile liquids, one of which is a solvent for the resin, and the other of which is not; the solvent having a more rapid rate of evaporation than the non-solvent. When a layer of such a solution is spread over a surface and permitted to dry, an opaque blushed film results.

The blushing technique has been practiced most extensively in the copy paper art. Heat-sensitive or pressuresensitive copy paper is prepared through the blushing technique by applying to a sheet of dark colored paper a thin layer of a blushing lacquer solution and permitting the solvent to evaporate. Blushable lacquer is applied to the surface of the paper at a wet coating thickness of about 0.5 to 2.0 mils at a solids content in the order of l0% and the resultant film is sufiiciently fragile to permit the resinous material to be coalesced under the influence of heat or pressure. Thus, when a sheet of copy paper carrying a blushed film is subjected to pressure as from a stylus, or is creased, the resinous material along the points where the pressure is applied or along the lines of the crease are coalesced, the film becomes transparent at such points and the dark paper under the film shows through. Similarly, in a heat sensitive copy paper coated with a blushed film, the resinous material can be coalesced along areas corresponding to dark areas of a graphic original through the thermographic process.

In the practice of our invention, a blushed cellular film is coated upon a porous flexible base to which it will adhere firmly but the walls of the cells that are distributed throughout the blushed coating are of a permanent character which will not collapse or coalesce under the conditions of temperature and pressure to which articles of apparel made of leather are normally subjected. The filmforming material that We employ in the practice of our invention is a thermoplastic elastomeric polyurethane. It

is a function of the base to which such elastomeric ma- 3 terial is applied to impart dimensional stability to the finished product without impairing its flexibility or breathability and without imparting undue bulk, a woven textile to which the polyurethane will adhere firmly being preferred.

In the method which we have invented of applying a water vapor permeable coating to a porous flexible base, a surface of the base is covered with a blushable coating comprising a thermoplastic elastomeric polyurethane uniformly distributed in a mixture of volatile liquids including a solvent and a non-solvent for the polyurethane. The solvent and non-solvent are miscible; and the non-solvent is less volatile than the solvent. The applied coating is blushed by removing substantially all of the volatile liquids by evaporation. The new leather subsitute that is produced by our method comprises a flexible porous base having firmly adhered thereto a breathable blushed coating of a thermoplastic elstomeric polyurethane having distributed therethrough interconneccted microporous spheroidal cells whose diameters range from about 0.1 to about 9 microns and said leather substitute having a moisture vapor transmission of from about 0.5 to about 4.0 g./ 10 cm. /24 hours. The range of moisture vapor transmission of leather is within the same range.

Our blushable coating may be applied to the base as a solution of the polyurethane in the volatile liquid mixture or as a colloidal dispersion of the polyurethane in such liquid, and the term uniformly distributed as used herein includes the solution state and the colloidal dispersion state of the polyurethane in the liquid.

Best results are achieved if the blushable coating is applied to the substrate at an elevated temperature. While the particular temperature selected is dependent upon the nature of the solvent, non-solvent and polyurethane, we have found that when using polyurethane in the solventnon-solvent combinations used in the examples which follow, the polyurethane is dissolved in the liquid portion of the blushable composition at a temperature which is preferably within the range of from 85 to 100 C. Preferably, suflicient polyurethane is dissolved to provide a 10 to 22% solids content solution. Since, the amount of solvent present, the amount of non-solvent present and the temperature are all variables which affect the solids content attainable, the proportions of solvent and non-solvent used should be selected to permit the 10 to 22% solids content at the solution temperatures.

We have made the surprising discovery that the blushable composition can be most easily and effectively applied to the substrate as a colloidal dispersion. Such a dispersion is produced by cooling the blushable solution until the composition assumes an opalescent or milky appearance. The composition may be coated at this point or more preferably, the temperature is allowed to drop another 2 to C. permitting the opalescence to become more pronounced before coating. The temperature at which the composition becomes opalescent will vary with the solids content and the proportions of solvent and non-solvent present, higher solids contents and higher non-solvent contents each generally tend toward opalescence at higher temperatures while lower solids contents and higher solvent contents each tend toward opalescence at lower temperatures. We preferably apply our coatings at a temperature of from to C. and, consequently prefer, proportions of solvents to non-solvents which produce opalescence within this temperature range at the above-mentioned range of solids contents. The proportions of solvent and non-solvent will vary with the nature of the solvent, non-solvent and polyurethane used. (It should be noted that unless otherwise indicated, all proportions used in this specification and claims are by weight.)

The composition may also be applied as a solution. However, such a method has several less than desirable features as compared to application of the composition as a colloidal dispersion. The solution flows and spreads too rapidly when applied. It is too low in viscosity to be con- 4 trollable in thickness of coating particularly at wet coating thicknesses of to 200 mils. In the colloidal dispersion state, the composition flows much more slowly; this is believed to be due to the thixotropic properties of the dispersion. The coating thickness may be readily controlled. Secondly, because of its low viscosity the solution tends to more readily penetrate the substrate and actually pass through the substrate to some extent resulting in undesirable strike-through. In addition, when the applied solutions are being drawn-down or leveled with doctor blades in the conventional manner, some streaking in the direction of draw-down has been noted. While these deficiencies render the solution application less desirable then the colloidal dispersion application in large scale commercial production, the deficiencies can be minimized in the production of the coated materials on carefully controlled smaller scale to produce desirable coated fabrics.

The polyurethanes used in the practice of this invention are thermoplastic elastomeric polyurethanes which are essentially linear in character. They are prepared from long chain diols such as linear polyesters and polyethers having molecular weights ranging from about 400 to 6000 and diisocyanates. The polyurethanes may also include in addition to the diols and diisocyanates, chain-extenders which are active hydrogen-containing difunctional compounds such as glycols, diamines, aminoalcohols and water.

The polyesters used in the preparation of the polyesterurethanes are prepared from the esterification of such dicarboxylic acids as adipic, succinic, pimelic, suberic, azelaic and sebacic or their anhydrides with glycols such as ethylene glycol, butanediol-l,4,hexa1nethylenediol-1,6, and octamethylenediol-l,8. In general, the glycol has the formula HO (CH XOH with x preferably from 2 to 10.

The polyethers used in the preparation of the polyetherurethanes involved in this invention may be characterized by the formulation HO(RO) H where R is a divalent alkylene radical and n is preferably a positive integer such that the molecular weight of the polyether lies between 400 and 6000. These polyethers are conventionally known as polyalkyleneether glycols or hydroxyl poly(alkylene oxides). Some conventional :polyethers which may be used are polyethyleneether glycol, polypropyleneether glycol, polytetramethyleneether glycol, polyhexamethyleneether glycol, polyoctamethyleneether glycol, polynonamethyleneether glycol, polydecamethyleneether glycol, polydodecamethyleneether glycol and mixtures thereof. Polyglycols containing several different radicals in the molecular chain such as, for example the compound HO(CH OC H O) H wherein n is an integer greater than 1 may also be used.

The diisocyanates may be aromatic, aliphatic, cycloaliphatic or mixtures thereof. They include naphthalene 1,5 diisocyanate, tetramethylene 1,4-diisocyanate, hexamethylene-1,6-diisocyanate, decamethylene-l,l0-diisocya-' OCN NCO wherein X may be a valence bond, an alkylene radical containing preferably 1 to 5 carbon atoms, NR where R is an alkyl radical, oxygen, sulfur, S0 and the like; and the isocyanate groups are preferably in a para-position. Most preferred are the diphenyl methane diisocyanates and excellent results are otbained from diphenyl methanep,p'-diisocyanate.

The polyurethanes may be chain-extended in the conventional manner by the conventional chain-extenders which have two active hydrogen atoms. The most preferable of the polyurethanes used in this invention are polyetherurethane and polyesterurethane in which glycols are used as chain-extenders. The chain-extension is preferably carried out by adding the polyester or polyether to the glycols preliminary to adding the diisocyanate to the mixture and then reacting the components. While any conventional hydroxyl terminated glycol may be used for chain-extension, the preferred glycols are straight chain glycols containing between 4 and car bons such as butanediol-1,4-hexamethylene glycol or any of the other 4-10 carbon glycols set forth above.

The preferred chain-extended polyurethanes which have given good results when used in the practice of this invention are the polyesterurethanes described in US. Pat. No. 2,871,218 and the polyetherurethanes described in U.S. Pat. No. 2,899,411. The polyetherurethanes of U.S. Pat. No. 2,899,411 are the reaction products of about 1 mole of polyalkyleneether glycol, about 0.5 to 9.0 moles of a 4 to 12 carbon atom aliphatic glycol and about from 1.5 to 10 moles of a diphenyl diisocyanate. The polyesterurethanes of US. Pat. No. 2,871,218 are prepared by reacting one mole of polyester having a molecular weight of about 600 to 1200 with about 1.1 to 3.1 moles .of a diphenyl diisocyanate in the presence of about 0.1

to 2.1 moles of a glycol containing about from 4 to 10 carbons. In both the polyesterurethane and polyetherurethane of these patents, the molar amount of the diisocyanate reacted is essentially equal to the total molar amount of the polyester or polyether plus the molar amount of the glycol chain-extender.

The polyurethanes may also be chain-extended with conventional diamine chain extenders such as hydrazine. Dinethyl piperazine and ethylene diamine may also be use Thermoplastic elastomeric polyurethanes which are not chain-extended will also be operable in the practice of this invention, e.g., the polyetherurethanes of US. Pat. 2,927,905.

The solvent used will depend on the polyurethane used as well as the nature of the non-solvent used since the solvent must be miscible with the non-solvent and must be more volatile than the non-solvent. Once a solvent is selected, potential non-solvents will be readily determinable by those skilled in the art of blushed coatings. Pyridine, dimethyl formamide, dimethyl sulfoxide, pyrrolidones, cyclohexanone and preferably tetrahydrofuran and pdioxane are suitable solvents for the polyesterurethanes and polyetherurethanes of Pats. 2,871,218 and 2,899,411 for example.

The non-solvent selected will depend on the polyurethane used and the nature of the solvent. The non-solvent must be a non-solvent for the polyurethane which is miscible with and less volatile than the solvent. While each of the following non-solvents will not be operable with each combination of solvent and polyurethane, they can be used in particular combinations: alkanols including butanol, hexanol and octanol, and aliphatic hydrocarbons particularly the aliphatic hydrocarbons with higher boiling ranges above 250 C. Of course, other non-solvents may be used, and these will be obvious to those skilled in the blushed coatings art.

While the base which we now prefer is a woven textile, non-woven textiles are utilizable. Cotton textiles have produced good results. However, any of a wide variety of natural and synthetic textiles to which the coating will adhere firmly will give satisfactory results e.g., nylon, polyesters such as Dacron materials, materials of acrylics such as Orlon, vinyl chloride copolymers, cellulosics such as rayon and cellulose acetate as well as natural materials such as cotton, wool, ramie, hemp and linen. The blushable coating is preferably applied at a wet coating thickness of from 20 to 200 mils, and most preferably at a thickness of 140-200 mils.

The polyurethanes used in this invention preferably have a molecular weight of from 5000 to 300,000 and most preferably from 40,000 to 80,000.

The breathability or moisture vapor transmission (M.V.T.) of leather and of the new coated fabrics that we have invented can be expressed in numerical terms determined as follows: The specimen under investigation is placed over the mouth of a Payne cup, which is circular and has an area of 10 square centimeters, so that it completely covers that mouth. The Payne cup contains 9 g. of 8 mesh calcium chloride granules. The covered cup is weighed and then exposed for 24 hours to a relative humidity of The cup is weighed again after ex posure and the gain in weight is noted. This gain in weight is the water vapor paassing through 10 square centimeters in 24 hours. Thus, a specimen of leather which has passed 2 g. of water vapor in 24 hours, has a M.V.T. of 2 g./ 10 cm. /24 hours. The M.V.T. values for leather and for our new leather substitute which are set forth herein are determined by following that procedure.

The coated fabrics described in this invention may be colored by the conventional methods for coloring leather.

In order that our invention will be fully available to those skilled in the art, the following specific examples are given:

EXAMPLE 1 40 g. of a polyetherurethane prepared from hydroxyl poly (tetramethylene oxide), diphenyl methane-p.p'-diisocyanate and butanediol-1,4 in accordance with the procedure set forth in US. Pat. No. 2,899,411, Example III are dissolved in 160 g. of p-dioxane. The solution is then heated to C. and maintained at 90 C. to 95 C. while 57.1 g. of an alkane hydrocarbon solvent having a boiling range of 350-388 F., a K.B. value of 27 and an aniline cloud point of 184.5 F. are added over a period of 12 minutes with continuous stirring. A solution which is clear to the eye forms. The solution is cooled. At 42 C., the so lution becomes opalescent. The composition is permitted to cool to 39 C. The composition is then coated at a thickness of W inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air-dried for a period of 16 hours at room temperature. Alternatively, the coating may be air-dried for about 1 /2 hours at room temperature and then for 2 hours at 65 C. After drying the coating has a thickness of about & inch, a hand closely resembling that of a leather, excellent scuff and abrasion resistance and a moisture vapor transmission or breathability equal to that of leather.

The coated fabric of this example passed 1.9 g. of water vapor in 24 hours. The M.V.T. of the fabric may be set forth as 1.9 g./ 10 cm. 24 hours as compared to leather which has an M.V.T. of 0.5 to 3.5 g./10 cm. /24 hours depending upon the type of leather.

The procedure described in the foregoing example may be repeated using a polyetherurethane of hydroxyl polytetramethylene oxide, diphenyl methane-p-,p'-diisocyanate and decanediol-1,10 prepared in accordance with the US. Pat. No. 2,889,411, Example II, and with the polyetherurethane of Example IV of said patent comprising hydroxyl poly (tetramethylene oxide), bitolylene diisocyanate and butanediol-1,4 with substantially the same results.

' EXAMPLE 2 40 g. of a polyetherurethane prepared in accordance with the method of preparing prepolymers set forth in US. Pat. No. 2,927,905, particularly Example V thereof except that a polyetramethylene ether glycol having a molecular weight of about 3,000 is used in place of the propylene oxide polyether are dissolved in g. of pdioxane. The solution is heated to and maintained at 90 C. While 64 g. of an alkane hydrocarbon solvent having a boiling range of 350-385 F., a K.B. value of 27 and an aniline cloud point of 184.5 F. are added over a period of 15 minutes With continuous stirring. An opalescent solution forms. The solution is cooled. The composition is permitted to cool to 40 C. and then coated at a thickness of inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air-dried for a period of 16 hours at room temperature. After drying, the coating has a thickness of about inch, a hand closely resembling that of a leather, excellent scuff and abrasion resistance and a moisture vapor transmission or breathability equal to that of leather.

The coated fabric of this invention passed 2.5 g. of water vapor in 24 hours. The M.V.T. of the fabric may be set forth as 2.5 g./ 10 om. /24 hours as compared to leather which has an M.V.T. of 0.5 to 3.5 g./l cm. 24 hours depending upon the type of leather.

EXAMPLE 3 A polyesterurethane having a molecular weight of about 60,000 is prepared following the procedure set forth in U.S. Pat. No. 2,871,218, col. 4, lines 13 to 27. A mixture of 1447 g. (1.704 mols) of hydroxyl poly (tetra- -methylene adipate), molecular weight 849, hydroxyl number 130.4, acid number 0.89, and 109.6 g. (1.218 mols) of butanediol-1,4 is melted in a four liter kettle and stirred with a spiral ribbon stirrer for about 20 minutes at a pressure of 5 to 6 mm. at 100 to 110 C. To this mixture, there is added 730 g. (2.92 mols) of diphenyl methanep,p diisocyanate. This mixture is stirred for about 1 minute and is then poured into a lubricated one gallon can which is promptly sealed with a friction top and the can placed in a 140 C. oven for 3.5 hours. The product is then cooled. A 20% solution of the polyesterurethane in p-dioxane is prepared.

Then 43.5 g. of the solution are heated to and maintained at 75 C. while 56.5 g. of nbutanol are added slowly. A cloudy mixture forms. The mixture is heated to 80 C. at which point, it becomes clear. Then the solution is cooled until it becomes opalescent. The opalescent composition is then coated at a thickness of inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air-dried for a period of 16 hours at room temperature. The coated surface has a hand closely resembling that of a leather, excellent scufi and abrasion resistance and a moisture vapor transmission or breathability equal to that of leather.

The coated fabric of this invention passed 2.7 g. of water vapor in 24 hours. The M.V.T. of the fabric may be set forth as 2.8 g./ 10 cm. /24 hours as compared to, leather which has an M.V.T. of 0.5 to 3.5 g./10' cm. /24 hours depending upon the type of leather EXAMPLE 4 The procedure described in Example 3 is repeated except that a solution of the polyesterurethane in tetrahydrofuran is used. Then 50 g. of the solution are heated to and maintained at C. while g. of nbutanol are added. The mixture is heated with stirring to about C. at which temperature the mixture is an opalescent dispersion. The dispersion is then coated at a thickness of 7 inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried for a period of 16 hours at room temperature. The coated surface has a hand closely resembling that of a leather, excellent scuff and abrasion resistance and a moisture vapor transmission or breathability equal to that of leather.

The coated fabric of this invention passed 2.7 g. of water vapor in 24 hours. The M.V.T. of the fabric may be set forth as 2.8 g./20 cm. /24 hours as compared to leather which has an M.V.T. of 0.5 to 3.5 g./l0 cm. /24 hours depending upon the type of leather 8 EXAMPLE 5 The procedure described in Example 3 is repeated using a 20% solution of the polyesterurethane in the p-dioxane. Then 400 g. of the solution are heated to and maintained at about C. while 53 g. of an alkane hydrocarbon solvent having a boiling range of 350-385 F., a K.B. value of 27 and an aniline cloud point of 184.5" F. are added over a period of 10 minutes. A cloudy or opalescent solution for-ms. The solution is cooled to 70 C. and coated at a thickness of A inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature. The coated surface has a hand closely resembling that of a leather good scuff and abrasion resistance and a moisture vapor transmission or breathability of about 0.9 g./l0 cm. 24 hours.

EXAMPLE 6 The procedure described in Example 3 is repeated using a 20% solution of the polyesterurethane in p-dioxan 150 g. of the solution are heated to and maintained at 9092 C. While cc. of n-hexanol are slowly added over a period of 15 minutes. The solution is clear. Then the solution is slowly cooled until opalescence appears at 42 C. The solution is cooled an additional 5 C. and coated at a thickness of inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature for a period of 10 hours followed by heating at 65.5 C. of about 1% hours. The coated surface has a hand closely resembling that of a leather, good scuff and abrasion resistance and a moisture vapor transmission of about 3.4 g./ 10 cm. 24 hours.

EXAMPLE 7 The procedure described in Example 2 is repeated using the same ingredients, procedure and proportions except that there is used a polyetherurethane made by heating equimolar proportions of hydroxyl (polytetramethylene oxide) M.W. 3020 and diphenyl methanep,p'-diisocyanate at about C. for about 2.5 hours.

The resulting coated fabric has all of the desirable properties of coated fabric of Example 2 and an M.V.T. of 2.12 g./10 cm. /24 hours.

EXAMPLE 8 The procedure described in Example 3 is repeated using a 20% solution of the polyesterurethane in p-dioxane. g. of the solution are heated to and maintained at 90 C. While 90 cc. of n-hexanol are slowly added over a period of 15 minutes. The solution is clear. Then, the solution is cooled until opalescence appears at 32 C. The solution is cooled to 14 C. and coated at a thickness of 1 inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature for a period of 10 hours followed by heating at 65.5 C. for about 1% hours. The coated surface has a hand closely resembling that of a leather, good scuff and abrasion resistance and a moisture vapor transmission of about 1.78 g./ 10 cm. 24 hours.

EXAMPLE 9 150 g. of 20% solution of the polyesterurethane described in Example 3 in p-dioxane is prepared and heated to and maintained at 90 C. while 110 cc. of n-hexanol are added. A clear solution forms. The solution is slowly cooled to 35 C. at which point opalescence appears. The opalescent solution is further cooled to 28 C. (room temperature) and coated at a thickness of inch onto the surface of a cotton sheet having a Weight of 0.002 ounce per square inch and air dried at room temperature for a period of 16 hours. The coated surface has a hand closely resembling that of leather, good scuff and abrasion resistance and a water vapor transmission of about 3.0 g./ 10 cmF/ 24 hours.

9 EXAMPLE 10 150 g. of a 20% solution of the polyesterurethane described in Example 3 in p-dioxane is prepared and heated to and maintained at 90 C. while 130 cc. of n-hexanol are added over a period of 17 minutes. A clear solution forms. The solution is cooled to 50 C. within about 10 minutes and still remains a clear solution. At this temperature, the solution is coated at a thickness of inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature. The coated surface has a hand similar to that of leather, good scuif and abrasion resistance and a moisture vapor transmission of about 3.2 g./l cm. /24 hours.

EXAMPLE 11 150 g. of a 20% solution of the polyesterurethane described in Example 3 are prepared. 90 cc. of n-hexanol are added over a period of about 25 minutes at room temperature and an opalescent dispersion forms. The composition is coated at a thickness of inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature. The coated surface has a hand closely resembling that of leather, good scuff and abrasion resistance and a moisture vapor transmission of about 3.3 g./l0 cmF/ 24 hours.

EXAMPLE 12 150 g. of a 20% solution of the polyesterurethane described in Example 3 in p-dioxane is prepared and heated to and maintained at 90 C. while 130 cc. of n-hexanol are added over a period of 32 minutes. A clear solution forms. This solution is maintained at approximately 90 C. for one hour with constant stirring. Then the solution is cooled until opalescence appears at 49 C. Cooling continued to 41 C. and the material coated at a wet thickness of 7 inch onto the surface of a cotton sheet having a weight of 0.002 ounce per square inch and air dried at room temperature for a period of 16 hours. The coated surface has a hand similar to that of leather, good scuff and abrasion resistance and a moisture vapor transmission of about 3.2 g./ 10 cm. /24 hours.

We have further found that films of the polyesterurethanes used in this invention unsupported by a substrate will also have leatherlike properties which approach the properties of the coated fabrics of this invention. In only two respects do these unsupported films have deficiencies as compared to the coated fabrics: their resistance to deformation through bending or creasing and their tear strength are not as good as the coated fabrics. However, in all other respects, the properties of these unsupported films are the equivalent of the coated fabrics and the films provide a very good leather substitute. The films are prepared by casting onto a conventional substrate like glass or steel. 1

EXAMPLE 13 150 g. of a 20% solution of the polyesterurethane de- I scribed in Example 3 are prepared and heated to 90 C. while 100 cc. of n-hexanol are added over a period of about 20 minutes. The solution is clear. Then, the solution is cooled until opalescence appears and then for an additional 5 degrees C. The solution is then cast at a thickness of inch onto a plate glass surface and air dried at room temperature for 40 hours and then dried at 150 F. for 2 hours. The film is removed. It has a hand closely resembling that of leather, good scuff and abrasion resistance and a moisture vapor transmission of 3.5 g./1O cm. /24 hours. Its resistance to permanent deformation through creasing or bending or its resistance to tearing while better than that of some leathers is not as good as the coated fabrics produced in accordance with Examples 1 through 5.

Films made in accordance with the method of Example 13 preferably have thicknesses in the range of from 20 to 60 mils.

While there have been described what is at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as it is defined in the following claims and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We claim:

1. The method of preparing a flexible sheet having leather-like properties which comprises applying a microporous water vapor permeable coating, which is crush resistant at ambient temperature, onto a porous flexible base which comprises covering a surface of said base with a blushable coating having a viscosity high enough to apply at a wet coating thickness of 20 to 200 mils, and comprising 10 to 22% by weight of a thermoplastic elastomeric polyurethane uniformly distributed in 78% by weight of a mixture of a volatile solvent for said polyurethane and a volatile liquid miscible with said solvent which liquid is a non-solvent for said polyurethane and is less volatile than said solvent and removing substantially all of the volatile mixture by evaporation.

2. The method of claim 1 wherein the polyurethane is distributed as a colloidal dispersion in the volatile mixture.

3. The method of claim 1 wherein said blushable coating is applied to said porous base at an elevated temperature.

4. The method of claim 2 wherein said blushable coating is applied to a textile substrate at an elevated temperature.

5. The method of claim 2 wherein said polyurethane is a polyesterurethane.

6. The method of claim 5 wherein said polyesterurethane is an essentially linear polyeterurethane elastomer which is the reaction product obtained by heating a mixture comprising as essentially polyurethane ingredients (1) one mol of an essentially linear hydroxyl terminated polyester of a saturated aliphatic glycol having from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms and a material selected from the group consisting of a dicarboxylic acid of the formula where R is an alkylene radical containing from 2 to 8 carbon atoms and its anhydride, said polyester having an average molecular weight between 600 and 1200 and having an acid number less than 10, and (2) from 1.1 to 3.1 mols of a diphenyl diisocyanate having an isocyanate group on each phenyl nucleus in the presence of (3) from about 0.1 to 2.1 mols of a saturated aliphatic free glycol containing from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms, the molar amount of said polyester and said free glycol combined being essentially equivalent to the molar amount of said diphenyl diisocyanate whereby there are essentially no groups of the class consisting of isocyanate and hydroxyl groups in said reaction products.

7. The method of claim 6 wherein said polyesterurethane is a linear hydroxyl terminated polyester produced by the reaction of hydroxyl polytetramethylene adipate and butanediol-1,4, and said diisocyanate is diphenyl methane-p,p'-diisocyanate.

8. The method of claim 2 wherein said polyurethane is a polyetherurethane.

9. The method of claim 8 wherein said polyetherurethane is the reaction product of an arylene diisocyanate and a polyalkyleneether glycol.

10. The method of claim 9 wherein said polyetherurethane is the reaction product of diphenyl methanep,p'-diisocyanate and polytetramethyleneether glycol.

11. The method of claim 9 wherein said polyetherurethane is the reaction product of an arylene diisocyanate,

11 a polyalkyleneether glycol and a saturated aliphatic glycol having from 4 to 12 carbon atoms, the molar amount of said polyalkyleneether glycol and said aliphatic glycol combined being substantially equivalent to the molar amount of said arylene diisocyanate.

12. The method of claim 11 wherein the reactants are diphenyl methane-p,p-diisocyanate, hydroxyl polytetramethylene oxide and butanediol-1,4.

13. The method of claim 11 wherein the reactants are bitolylene diisocyanate, hydroxyl polytetramethylene oxide and butanediol1,4.

14. A method for making a water vapor permeable coated fabric comprising preparing a composition having a viscosity high enough to apply at a wet coating thickness of 20 to 200 mils by dissolving 10 to 22% by weight, of a thermoplastic elastomeric polyurethane in 90 to 78%, by weight, of a mixture of a volatile solvent for said polyurethane and a volatile liquid which is a non-solvent for said polyurethane and is less volatile than said solvent by heating to a temperature at which the mixture containing the polyurethane is clear to the eye, lowering the temperature until a colloidal dispersion of the polyurethane in the volatile mixture forms, coating said colloidal dispersion onto the surface of a textile substrate and removing substantially all of the volatile mixture by evaporation.

15. The method of claim 14 wherein the temperature at which the colloidal dispersion forms is an elevated temperature.

16. A composite flexible sheet having leather-like properties comprising a porous flexible base having firmly adhered thereto a breathable microporous, vapor permeable coating, which is crush resistant at ambient temperatures, said coating consisting essentially of a thermoplastic elastomeric polyurethane having distributed therethrough interconnected. microporous spheroidal cells the average diameter of which ranges from about 0.1 to about 9 microns, said composite sheet having a moisture vapor transmission of from 0.9 to 4.0 g./ 10 cm. /24 hours, and said composite sheet being of sufiicient thickness to be used as a substitute for leather in shoe uppers.

17. The composite sheet of claim 16 wherein said polyurethane is a polyesterurethane.

18. The composite sheet of claim 17 wherein said polyesterurethane is an essentially linear polyesterurethane elastomer which is the reaction product obtained by heating a mixture comprising as essential polyurethane ingredients (1) one mol of an essentially linear hydroxyl terminated polyester of a saturated aliphatic glycol having from 4 to 10 carbon atoms and having hydroxyl groups on its terminal carbon atoms and a material selected from the group consisting of a dicarboxylic acid of the formula where R is an alkylene radical containing from 2 to 8 carbon atoms and its anhydride, said polyester having an average molecular weight between 600 and 1200 and having an acid number less than 10, and (2) from 1.1 to 3.1 mols of a diphenyl diisocyanate having an isocyanate group on each phenyl nucleus in the presence of (3) from about 0.1 to 2.1 mols of a saturated aliphatic free glycol esterurethane is a linear hydroxyl terminated polyester produced by the reaction of hydroxyl polytetramethylene adipate and butanediol-1,4, and said diisocyanate is diphenyl methane-p,p-diisocyanate.

20. The composite sheet of claim 16 wherein said polyurethane is a polyetherurethane'.

21. The composite sheet of claim 20 wherein said polyetherurethane is the reaction product of an arylene diisocyanate and a polyalkyleneether glycol.

22. The composite sheet of claim 21 wherein said polyetherurethane is the reaction product of diphenyl methane-' etherurethane is the reaction product of an arylene di-.

isocyanate, a polyalkyleneether glycol and a saturated aliphatic glycol having from 4 to 12 carbon atoms, the molar amount of said polyalkyleneether glycol and said aliphatic glycol combined 7 being substantially equivalent to the molar amount of said arylene diisocyanate.

24. The composite sheet of claim 23 wherein the reactants are diphenyl methane-p,p-diisocyanate, hydroxyl polytetramethylene oxide and butanediol-l,4.

25. The composite sheet of claim 23 wherein the reactants are bitolylene diisocyanate, hydroxyl polytetramethylene oxide and butanediol-1,4.

26. A method of forming a tough water vapor permeable flexible sheet or film having leather-like properties which comprises casting a microporous, vapor permeable coating, which is crush resistant at ambient temperatures, onto a support, said coating comprising a blushable coating having a wet coating thickness of 20 to 200 mils and comprising 10 to 22% by weight of a thermoplastic elastomeric polyurethane uniformly distributed in to 78% by weight of a mixture of a volatile solvent for said polyurethane and a volatile liquid miscible with said solvent which liquid is a non-solvent for said polyurethane and is less volatile than said solvent and removing substantially all of the volatile mixture by evaporation, and thereafter stripping the film from said support.

27. A flexible sheet having leather-like properties, which consists essentially of an unsupported, microporous, vapor permeable, film of thermoplastic polyurethane, which is crush resistant at ambient temperatures, said sheet having distributed therethrough interconnected microporous spheroidal cells the average diameters of which range from about 0.1 to about 9 microns, said sheet having a moisture vapor transmission of from 0.9 to 4.0 g.

cm. 24 hours, and said sheet being of sufficient thickness to be used as a substitute for leather in shoe uppers. 28. The sheet of claim 27 wherein the thickness of the film is in the range of from 20 to 60' mils.

References Cited UNITED STATES PATENTS 2,899,411 8/ 1959 Schollenberger 2-6077.5 2,901,467 8/1959 Croco 1l716lX 2,927,905 3/1960 Eckert 260-22X 3,000,757 9/1961 Johnston et al. 117- 63 3,100,721 8/1963 Holden -l17135.5 3,180,853 4/19'65 Peters 1l7161X 3,222,208 12/1965 Bertollo 11763 3,322,568 5/1967 Golodner 117135.5

WILLIAM D. MARTIN, Primary Examiner T. G. DAVIS, Assistant Examiner US. Cl. X.R. 

